Editing Io (programming language) (section)

=== Examples ===
The ubiquitous [[Hello world program]]:

<syntaxhighlight lang="io">
 "Hello, world!" println
</syntaxhighlight>

New objects are created by [[Cloning (programming)|cloning]] objects. In Io specifically, a new, empty object is created and only the differences between it and its parent are stored within the new object; this behavior is known as [[differential inheritance]]. An example of this behavior is shown:

<syntaxhighlight lang="io">
 A := Object clone         // creates a new, empty object named "A"
</syntaxhighlight>

A simple non-recursive factorial function, in Io:

<syntaxhighlight lang="io">
factorial := method(n,
    if(n == 0, return 1)
    res := 1
    Range 1 to(n) foreach(i, res = res * i)
)
</syntaxhighlight>

Because assignment of <code>res * i</code> to <code>res</code> is the last action taken, the function implicitly returns the result and so an explicit return expression is not needed. The above demonstrates the usage of [[Range (computer programming)|ranges]], and doesn't use a <code>for()</code> loop, which would be faster.